Modern attitudes toward homosexuality have religious, legal, and medical underpinnings.
Before the High Middle Ages, homosexual acts appear to have been tolerated or ignored by the Christian church throughout Europe.
Beginning in the latter twelfth century, however, hostility toward homosexuality began to take root, and
eventually spread throughout European religious and secular institutions.
Condemnation of homosexual acts (and other nonprocreative sexual behavior) as "unnatural,"
which received official expression in the writings of Thomas Aquinas and others, became widespread and has continued through the present
day (Boswell, 1980).
[Bibliographic references are on a different web page]

Religious teachings soon were incorporated into legal sanctions.
Many of the early American colonies, for example, enacted stiff criminal penalties for sodomy,
an umbrella term that encompassed a wide variety of sexual acts that were nonprocreative (including
homosexual behavior),
occurred outside of marriage (e.g., sex between a man and woman who were not married),
or violated traditions (e.g., sex between husband and wife with the woman on top).
The statutes often described such conduct only in Latin or with oblique phrases such as
"wickedness not to be named").
In some places, such as the New Haven colony, male and female homosexual acts were punishable by death (e.g., Katz, 1976).

By the end of the 19th century, medicine and psychiatry were effectively competing with religion and the law for jurisdiction over sexuality.
As a consequence, discourse about homosexuality expanded from the realms of sin and crime to include that of pathology.
This historical shift was generally considered progressive because a sick person was less blameful than a sinner or criminal
(e.g., Chauncey, 1982/1983; D'Emilio & Freedman, 1988; Duberman, Vicinus, & Chauncey, 1989).

Even within medicine and psychiatry, however, homosexuality was not universally viewed as a pathology.
Richard von Krafft-Ebing described it as a degenerative sickness in his Psychopathia Sexualis,
but Sigmund Freud and Havelock Ellis both adopted more accepting stances.
Early in the twentieth century, Ellis (1901) argued that homosexuality was inborn and therefore not immoral, that it was not a disease, and that many homosexuals made outstanding contributions to society (Robinson, 1976).

Sigmund Freud

Sigmund Freud's basic theory of human sexuality was different from that of Ellis.
He believed all human beings were innately bisexual, and that they become heterosexual or homosexual as a result of their experiences with parents and others (Freud, 1905).
Nevertheless, Freud agreed with Ellis that a homosexual orientation should not be viewed as a form of pathology.
In a now-famous letter to an American mother in 1935, Freud wrote:

"Homosexuality is assuredly no advantage, but it is nothing to be ashamed of,
no vice, no degradation, it cannot be classified as an illness;
we consider it to be a variation of the sexual function produced by a certain arrest of sexual development.
Many highly respectable individuals of ancient and modern times have been homosexuals,
several of the greatest men among them (Plato, Michelangelo, Leonardo da Vinci, etc.).
It is a great injustice to persecute homosexuality as a crime, and cruelty too....

"If [your son] is unhappy, neurotic, torn by conflicts, inhibited in his social life,
analysis may bring him harmony, peace of mind, full efficiency whether he remains a homosexual or gets changed...."
(reprinted in Jones, 1957, pp. 208-209, from the American Journal of Psychiatry, 1951, 107, 786).

Later psychoanalysts

Later psychoanalysts did not follow this view, however.
Sandor Rado (1940, 1949) rejected Freud's assumption of inherent bisexuality,
arguing instead that heterosexuality is natural and that homosexuality is a "reparative" attempt to achieve sexual pleasure when normal heterosexual outlet proves too threatening.
Other analysts later argued that homosexuality resulted from pathological family relationships during the oedipal period
(around 4-5 years of age) and claimed that they observed these patterns in their homosexual patients (Bieber et al., 1962).
Charles Socarides (1968) speculated that the etiology of homosexuality was pre-oedipal and, therefore, even more pathological than had been supposed by earlier
analysts (for a detailed history, see Lewes, 1988; for briefer summaries, see Bayer, 1987; Silverstein, 1991).

Biases in psychoanalysis

Although psychoanalytic theories of homosexuality once had considerable influence in psychiatry and in the larger culture, they were not subjected to rigorous empirical testing.
Instead, they were based on analysts' clinical observations of patients already known by them to be homosexual.

This procedure compromises the validity of the psychoanalytic conclusions in at least two important ways.
First, the analyst's theoretical orientations, expectations, and personal attitudes are likely to bias her or his observations.
To avoid such bias, scientists take great pains in their studies to ensure that the researchers who actually collect the data do not have expectations about how a particular research participant will respond.
An example is the "double blind" procedure used in many experiments.
Such procedures have not been used in clinical psychoanalytic studies of homosexuality.

A second problem with psychoanalytic studies is that they have only examined homosexuals who were already under psychiatric care 
in other words, homosexuals who were seeking treatment or therapy.
Patients, however, cannot be assumed to be representative of the general population.
Just as it would be inappropriate to draw conclusions about all heterosexuals based only on data from heterosexual psychiatric patients,
we cannot generalize from observations of homosexual patients to the entire population of gay men and lesbians.

Alfred Kinsey

A more tolerant stance toward homosexuality was adopted by researchers from other disciplines.
Zoologist and taxonomist Alfred C. Kinsey, in his groundbreaking empirical studies of sexual behavior among American adults,
revealed that a significant number of his research participants reported having engaged in homosexual behavior to the point of orgasm after age 16
(Kinsey, Pomeroy, & Martin, 1948; Kinsey, Pomeroy, Martin, & Gebhard, 1953).
Furthermore, Kinsey and his colleagues reported that 10% of the males in their sample and 2-6% of the females
(depending on marital status) had been more or less exclusively homosexual in their behavior for at least three years between the ages of 16 and 55.

Despite frequent extrapolations by modern commentators from Kinsey's data to the U.S. adult population,
the representativeness of his nonprobability sample cannot be assessed
(for methodological and statistical critiques, see Terman, 1948; Cochran, Mosteller, &
Tukey, 1954; Wallis, 1949).
Nevertheless, his work revealed that many more American adults than previously suspected had engaged in
homosexual behavior or had experienced same-sex fantasies.
This finding cast doubt on the widespread assumption that homosexuality was practiced only by
a small number of social misfits.1

Comparative studies

Other social science researchers also argued against the prevailing negative view of homosexuality.
In a review of published scientific studies and archival data,
Ford and Beach (1951) found that homosexual behavior was widespread among various nonhuman species
and in a large number of human societies.
They reported that homosexual behavior of some sort was considered normal and socially acceptable
for at least some individuals in 64% of the 76 societies in their sample;
in the remaining societies, adult homosexual activity was reported to be totally absent, rare, or carried on only in secrecy.

As with Kinsey, whether this proportion applies to all human societies cannot be known because
a nonprobability sample was used.
However, the findings of Ford and Beach demonstrate that homosexual behavior occurs in many societies
and is not always condemned (see also Herdt, 1984; Williams, 1986).

Military research

Although dispassionate scientific research on whether homosexuality should be viewed as an illness was largely
absent from the fields of psychiatry, psychology, and medicine during the first half of the twentieth century,
some researchers remained unconvinced that all homosexual individuals were mentally ill or socially misfit.
Berube (1990) reported the results of previously unpublished studies conducted by
military physicians and researchers during World War II.
These studies challenged the equation of homosexuality with psychopathology, as well as the stereotype
that homosexual recruits could not be good soldiers.

A common conclusion in their wartime studies was that,
in the words of Maj. Carl H. Jonas, who studied fifty-three white and seven black men at Camp Haan,
California, "overt homosexuality occurs in a heterogeneous group of individuals."
Dr. Clements Fry, director of the Yale University student clinic, and Edna Rostow,
a social worker, who together studied the service records of 183 servicemen,
discovered that there was no evidence to support the common belief that
"homosexuality is uniformly correlated with specific personality traits"
and concluded that generalizations about the homosexual personality
"are not yet reliable."

.... Sometimes to their amazement, [researchers] described what they called the
"well-adjusted homosexuals" who, in [William] Menninger's words,
"concealed their homosexuality effectively and, at the same time, made creditable records
for themselves in the service."
Some researchers spoke in glowing terms of these men.
"The homosexuals observed in the service," noted Navy doctors Greenspan and Campbell,
"have been key men in responsible positions whose loss [by discharge] was acutely felt in their respective departments."
They were "conscientious, reliable, well-integrated and abounding in emotional feeling
and sincerity."
In general, "the homosexual leads a useful productive life, conforming with all dictates of the community,
except its sexual requirements" and was "neither a burden nor a detriment to society."
Fry and Rostow reported that, based on evidence in service records, homosexuals were no better or worse
than other soldiers and that many "performed well in various military jobs" including combat
(Berube, 1990, pp. 170-171, footnotes omitted).

Today, a large body of published empirical research clearly
refutes the notion that homosexuality per se is indicative of or correlated with psychopathology.
One of the first and most famous published studies in this area was conducted by psychologist Evelyn Hooker.

Hooker's study

Hooker's (1957) study was innovative in several important respects.
First, rather than simply accepting the predominant view of homosexuality as pathology,
she posed the question of whether homosexuals and heterosexuals differed in their
psychological adjustment.
Second, rather than studying psychiatric patients, she recruited a sample of
homosexual men who were functioning normally in society.
Third, she employed a procedure that asked experts to rate the adjustment of men
without prior knowledge of their sexual orientation.
This method addressed an important source of bias that had vitiated so many previous studies
of homosexuality.

Hooker administered three projective tests (the Rorschach, Thematic Apperception Test [TAT],
and Make-A-Picture-Story [MAPS] Test) to 30 homosexual males and 30 heterosexual males
recruited through community organizations.
The two groups were matched for age, IQ, and education.
None of the men were in therapy at the time of the study.

Unaware of each subject's sexual orientation, two independent Rorschach experts
evaluated the men's overall adjustment using a 5-point scale.
They classified two-thirds of the heterosexuals and two-thirds of the homosexuals in the
three highest categories of adjustment.
When asked to identify which Rorschach protocols were obtained from homosexuals,
the experts could not distinguish respondents' sexual orientation at a level better than chance.

A third expert used the TAT and MAPS protocols to evaluate the psychological adjustment of the men.
As with the Rorschach responses, the adjustment ratings of the homosexuals and heterosexuals did not differ significantly.

Hooker concluded from her data that homosexuality is not a clinical entity and
that homosexuality is not inherently associated with psychopathology.

Hooker's findings have since been replicated by many other investigators using a variety of research methods.
Freedman (1971), for example, used Hooker's basic design to study lesbian and heterosexual women.
Instead of projective tests, he administered objectively-scored personality tests to the women.
His conclusions were similar to those of Hooker.

Although some investigations published since Hooker's study have claimed to support the view of
homosexuality as pathological, they have been methodologically weak.
Many used only clinical or incarcerated samples, for example,
from which generalizations to the population at large are not possible.
Others failed to safeguard the data collection procedures from possible biases by the
investigators 
for example, a man's psychological functioning would be evaluated by his own psychoanalyst,
who was simultaneously treating him for his homosexuality.

Some studies found differences between homosexual and heterosexual respondents,
and then assumed that those differences indicated pathology in the homosexuals.
For example, heterosexual and homosexual respondents might report different kinds of childhood experiences
or family relationships.
It would then be assumed that the patterns reported by the homosexuals indicated pathology,
even though there were no differences in psychological functioning between the two groups.

The weight of evidence

In a review of published studies comparing homosexual and heterosexual samples on psychological tests,
Gonsiorek (1982) found that, although some differences have been observed in test results
between homosexuals and heterosexuals, both groups consistently score within the normal range.
Gonsiorek concluded that "Homosexuality in and of itself is unrelated to psychological disturbance or maladjustment.
Homosexuals as a group are not more psychologically disturbed on account of their homosexuality"
(Gonsiorek, 1982, p. 74; see also reviews by Gonsiorek, 1991; Hart, Roback, Tittler, Weitz, Walston & McKee, 1978; Riess, 1980).

Confronted with overwhelming empirical evidence and changing cultural views of homosexuality,
psychiatrists and psychologists radically altered their views, beginning in the 1970s.

Removal from the DSM

In 1973, the weight of empirical data, coupled with changing social norms and the development
of a politically active gay community in the United States, led the Board of Directors of the
American Psychiatric Association
to remove homosexuality from the
Diagnostic and Statistical Manual of Mental Disorders (DSM).
Some psychiatrists who fiercely opposed their action subsequently circulated a petition calling for a vote on the issue by the Association's membership.
That vote was held in 1974, and the Board's decision was ratified.

Subsequently, a new diagnosis, ego-dystonic homosexuality, was created for the
DSM's third edition in 1980.
Ego dystonic homosexuality was indicated by:
(1) a persistent lack of heterosexual arousal, which the patient experienced as interfering with
initiation or maintenance of wanted heterosexual relationships, and
(2) persistent distress from a sustained pattern of unwanted homosexual arousal.

This new diagnostic category, however, was criticized by mental health professionals on numerous grounds.
It was viewed by many as a political compromise to appease those psychiatrists  mainly
psychoanalysts  who still considered homosexuality a pathology.
Others questioned the appropriateness of having a separate diagnosis
that described the content of an individual's dysphoria.
They argued that the psychological problems related to ego-dystonic homosexuality
could be treated as well by other general diagnostic categories,
and that the existence of the diagnosis perpetuated antigay stigma.

Moreover, widespread prejudice against homosexuality in the United States
meant that many people who are homosexual go through an initial phase in which
their homosexuality could be considered ego dystonic. According to
the American Psychiatric Association, "Fears and misunderstandings about homosexuality are widespread.... [and] present daunting challenges to the development and maintenance of a positive self-image in gay, lesbian and bisexual persons and often to their families as well."

In 1986, the diagnosis was removed entirely from the DSM.
The only vestige of ego dystonic homosexuality in the revised DSM-III
occurred under Sexual Disorders Not Otherwise Specified, which
included persistent and marked distress about one's sexual orientation
(American Psychiatric Association, 1987;
see Bayer, 1987, for an account of the events leading up to the 1973 and 1986 decisions).

The American Psychological Association (APA) promptly endorsed the psychiatrists' actions,
and has since worked intensively to eradicate the stigma historically associated
with a homosexual orientation (APA, 1975; 1987).

Conclusion

Some psychologists and psychiatrists still hold negative personal attitudes toward homosexuality.
However, empirical evidence and professional norms do not support the idea that
homosexuality is a form of mental illness or is inherently linked to psychopathology.

The foregoing should not be construed as an argument that sexual minority individuals are free from
mental illness and psychological distress.
Indeed, given the stresses created by sexual stigma and prejudice,
it would be surprising if some of them did not manifest psychological problems (Meyer, 2003).
The data from some studies suggest that, although most sexual minority individuals are well adjusted,
nonheterosexuals may be at somewhat heightened risk for depression, anxiety, and related problems,
compared to exclusive heterosexuals (Cochran & Mays, 2006).

Unfortunately, because of the way they were originally designed, most of these studies do not yield
information about whether and to what extent such risks might be greater for various subgroups
within the sexual minority population
(e.g., individuals who identify as lesbian, gay, or bisexual versus those who do not;
bisexuals versus lesbians and gay men).
In future research, it will be important to compare different sexual minority groups in order to
understand how so many individuals withstand the stresses imposed by sexual prejudice, and to identify
effective strategies for treating those with psychological problems.

Although Kinsey's studies are often cited as documenting that 10% of the U.S. population is gay,
Kinsey did not categorize his research participants according to sexual orientation.
Instead, he chose to emphasize sexual behavior and fantasy.
In addition, because Kinsey did not collect his data from a probability sample,
valid inferences cannot be made from them to the larger population.

For a discussion of how the Kinsey data came to be widely understood as supporting the
ten percent figure, see Voeller (1990).
Support for the ten percent figure was also provided by Paul Gebhard
(director of the Kinsey Institute) in a 1977 memo to the National Gay Task Force.

All surveys are likely to underestimate the actual prevalence of homosexuality because,
fearing discrimination and stigma, many gay respondents are reluctant to tell a stranger
(even anonymously) that they are homosexual (e.g., Villarroel et al., 2006).
Recognizing this limitation, most research with probability samples suggests that at least
3-6% of the US adult male population is homosexual, with somewhat fewer females
(Fay, Turner, Klassen, & Gagnon, 1989; Hatfield, 1989; Laumann, Gagnon, Michael, & Michaels, 1994; Lever & Kanouse, 1996; Rogers & Turner, 1991).